Hamilton delivered a flawless triumphant drive at the Circuit of the Americas to get his 50th Grand Prix win.
Lewis Hamilton joined an elite club on Sunday when he claimed his 50th Formula One victory at the United States Grand Prix but admitted he fears that another reliability issue will wreck his bid for a fourth world title.
The defending three-time world champion delivered a flawless triumphant drive at the Circuit of the Americas to join seven-time champion Michael Schumacher and four-time champion Alain Prost as a winner of 50 or more races.
Schumacher won a total of 91 Grands Prix and Prost 51.
"That's been a long time coming that one," said Hamilton. "It's been a long hard slog for me, but I tell you that in the race I was worried about reliability all the way through.
"It was in my mind all through the race."
Hamilton has suffered from engine failures, mechanical problems and bad starts throughout the season and knows that one more failure, at next weekend's Mexican Grand Prix, could hand the drivers' crown to his Mercedes team-mate Nico Rosberg.
If Rosberg, who now leads by 26 points with three races to go, wins in Mexico and Hamilton has to retire, or fails to score a point, he will take the title.
Hamilton, however, is determined to remain positive.
"I was down on power today and that worried me, but it is a great result for the team. For me, it is nice to have a have a good solid weekend.
"And also a good start! I just hope it continues like this. I just felt so much more confident thanks to a few things we changed when I was at the factory last week.
"I felt more comfortable at the start but I was worrying all the time. Reliability was the only thing on my mind."
Hamilton has scored his 50 wins from 185 races compared to Schumacher with 153 and Prost in 192.
Rosberg finished second on Sunday after falling to third at the first corner when Daniel Ricciardo of Red Bull passed him.
He regained his place thanks to a pit stop during a Virtual Safety Car (VSC) intervention later in the race while Ricciardo went onto finish third.
Rosberg said: "I lost out a bit at the start, but I gave everything to come back and I was going flat out all the way right to the end."
He finished five seconds behind Hamilton who had controlled the race from lights to flag.